Carrier 30PA Installation, Operation And Maintenance Instructions page 26

Ductable air-cooled scroll
chillers and heat pumps
 Adjustment of the water fl ow
- The fi lling of the hydraulic circuit is then carried out:
• Open the water circuit valves and ensure that the water circulates
around the exchanger with the pump in service.
• Bleed the air in the hydraulic circuit.
• Verify the operation of the water circulation controller and the cold/
hot water control.
- Factory set confi guration:
• Thermal jump: 5ºC
• COOLING mode operation: 12ºC / 7ºC
• HEATING mode operation: 40ºC / 45ºC
Operation is recommended with the emitters closed.
Note: other control values are allowed once the verifi ed fl ow and
temperatures remain within the operational limits of the unit.
- The total pressure drop in the installation is not known precisely at
start-up, such that it is necessary to adjust the water fl ow with the
regulation valve in order to obtain the desired nominal fl ow.
- Thanks to the pressure drop generated in the hydraulic network,
this regulation valve allows the network's pressure/fl ow curve to be
overlapped with the pump's pressure/fl ow curve, thereby obtaining
the nominal fl ow corresponding to the desired operating point.
- The reading of the pressure drop in the plate exchanger (which is
obtained by connecting two pressure gauges on the unit's inlet and
outlet) will be used as a means of control and adjustment of the
nominal fl ow of water in the installation.
- Next the following procedure must be performed:
• Totally open up the regulation valve.
• Leave the pump running for 2 hours in order to eliminate any
possible solid particles present in the circuit.
• Read the pressure drop of the plate exchanger when starting up
the pump and 2 hours later.
• If the pressure drop has decreased, this means that the mesh fi lter
is obstructed; it must be disassembled and cleaned.
• Repeat until the obstruction is eliminated from the fi lter.
• Once the circuit is free of contaminating elements, read the
pressure drop of the plate exchanger and compare it with the
theoretical pressure drop of the selection.
If the value is greater than the theoretical value, the fl ow is too
high. The pump offers too high of a fl ow from the point of view of
the installation's pressure drop. In that case, close the regulation
valve one revolution and read the new pressure drop. Perform a
successive approximation by closing the regulation valve until the
nominal fl ow is obtained at the desired operating point.
On the contrary, if the network's pressure drop is too high with
regards to the available static pressure offered by the pump,
the resulting water fl ow will be reduced and the temperature
difference between the inlet and outlet of the exchanger will be
more signifi cant, which is why it will be necessary to minimize
the pressure drops.
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 Control of the refrigerant load
- When starting the compressor, check the subcooling and overheating
and thus verify is the refrigerant load is appropriate to the operation
conditions.
- If the refrigerant load is lower than required, the suction pressure
will be rather lower than normal, and overheating when suctioning
from the compressors will be high. This can cause an interruption
in operation due to activation of the refrigerant load safety device.
To adjust the refrigerant load, a schrader valve is built into the unit on
the liquid line.
Indoor circuit
water inlet
Revovery circuit
water outlet
Low-pressure schrader valve
(optional pressure gauge connection)
Low-pressure
pressostat
High-pressure
pressostat
High-pressure schrader
valve (optional pressure
gauge connection)
Revovery circuit
water inlet
Indoor circuit
water outlet
Door
switch
Electric
panel